Rotary lobe pumps are known. Lobe pumps are ideal for pumping shear-sensitive products because the rotating lobes or rotors do not engage one another. Instead, when a lobe pump is properly timed, the rotors make no contact with each other. Accordingly, shear sensitive fluids may be pumped with minimal shear forces imposed on the fluids by the rotors. Traditionally, rotary lobe pumps have been used in sanitary applications, including food and health care products. The pumping chambers are sealed for sanitary reasons and the drive and driven shafts are supported with bearings disposed outside of the pump chamber.
In some lobe pump designs, the rotors are fixedly mounted onto a shaft which passes through the rotor case. The shaft passes through a sleeve support which, in turn, is connected to the rotor case. Because the shaft rotates within the sleeve support and the outside diameter of the shaft and the inside diameter of the sleeve support are closely matched, the positioning of sealing members between the shaft and sleeve support is not possible. However, the positioning of seals between the sleeve support and the rotor case is feasible. In order to prevent fluid from migrating between the shaft and sleeve support, an effective sealing mechanism must be placed between the sleeve support and an inside surface of the rotor. This is problematic because most sealing mechanisms are designed to seal radially inward. However, in the case of rotary lobe pumps employing a sleeve support through which the shaft passes, the sleeve support is stationary and disposed radially inside of an opposing portion of the rotor. Therefore, there is a need for an improved sealing mechanism or seal assembly for mounting on a stationary sleeve support and extending radially outwardly for sealing in a radially outward direction against an inside surface of a rotating rotor.
Further, rotary lobe pumps are typically designed to be coupled with motors of a variety of types. Because motor drives, such as hydraulic motor drives, different motor drives can require different drive shaft designs for the rotary lobe pump. Accordingly, the pump manufacturer must be able to provide a variety of drive shafts for its pump to enable its pumps to be utilized with a wide variety of drive mechanisms. In order to avoid the expense and inconvenience of providing a number of different drive shafts for each rotary lobe pump, manufacturers need a reliable adapter system to enable a single drive shaft to be coupled to a variety of motor drives.
Another problem associated with the use of rotary lobe pumps is the timing or synchronization of the contra-rotating rotors. As noted above, the timing must be exact so that clearances are maintained to prevent rotor-to-rotor contact. The requirement of precise timing makes the assembly of rotary lobe pumps time consuming and, therefore, expensive. Further, because the timing gears are typically fixedly mounted to the drive and driven shafts, the entire shaft assembly must be rotated during the timing adjustment process. Accordingly, there is a need for an improved timing gear/shaft design which enables either the timing gears or the shafts to be rotated during the timing adjustment instead of current designs which require the entire shaft/timing gear assembly to be rotated. By permitting the operator to rotate only the timing gears, the timing adjustment process could be shortened and therefore manufacturing costs could be reduced.
A need also arises when it is desired to change the timing gears during the working life of the pump. Specifically, it may be desirable to switch from a straight timing gear to a slanted or herringbone type timing gear. Thus, there is a need for a timing gear configuration whereby the timing gears can be easily replaced.
Still another problem that arises with the seals of rotary lobe pumps and other pumps is the difficulty in changing the seals or servicing the seals. Often, the pump must be substantially disassembled which requires that the pump be taken out of service. Accordingly, there is a need for an improved pump whereby the seals disposed between the shaft and the rotor can be quickly and easily changed or serviced on-site and without the need for taking the pump out of service.
Further, there is a need for a rotary lobe pump whereby the shaft/rotor seals can be easily accessed for repair and maintenance with a minimum of pump disassembly.